It is known in the art to produce high modulus organic fibers from linear polymers, such as aramids or wholly aromatic polyesters. These polymers, which can be utilized in solution or in melt form, exhibit nematic mesophase properties. That is, in the phase intermediate the liquid and solid phases of the polymer, the molecules are arranged in parallel lines. As a result of this molecular arrangement, the fibers possess highly anisotropic mechanical properties which is reflected by their high strength in the direction of molecular orientation but poor strength in all other directions. As a result of this weakness, the fibers tend to shred easily and have poor abrasion resistance.
A different class of mesophase forming polymers have recently been developed. These polymers are described as "comb polymers" since they possess mesophase forming side chains branching off a conventional backbone. The interaction of these side chains causes the polymer to exhibit smectic rather than nematic properties which alleviates some of th problems discussed above by adding an additional degree of order.
One such polymer, polymethacryloyloxybenzoic acid, is described in the following articles: Amerik et al, "polymerization of p-Methacryloyloxybenzoic Acid in Mesomorphic and in Liquid States", J. Poly Sci., Part C., No. 23, pp. 231-238 (1968); Blumstein et al, "Polymerization of p-Methacryloyloxy Benzoic Acid With Liquid Crystalline Media", in Liquid Crystals 3, Part II, pp. 1075-1087 (Brown and Labes, Ed., Gordon and Breach Science Publishers, New York, N.Y., 1971); Blumstein et al, "Crystallinity and Order in Atactic Poly (acryloyloxybenzoic acid) and Poly (methacryloyloxybenzoic acid), Macromolecules, Vol. 9, No. 2, pp. 243-247 (March-April 1976); and Blumstein et al., "Oriented Polymer Growth in Thermotropic Mesophases", Macromolecules, Vol. 8, No. 1, pp. 73-76 (1975).
Unfortunately, the comb polymers are difficult to fashion into desired end products. For example, with the exception of ultra high molecular weight polymethacryloyloxybenzoic acid, the comb polymers yield an anisotropic melt which tends to decompose. While not all of the polymers decompose to the same extent, this feature makes it difficult to form end products from the polymer melt.
In commonly assigned U.S. Pat. application Ser. No. 871,282 filed concurrently herewith by Eui Won Choe entitled "Ultra-High Molecular Weight Polymethacryloyloxybenzoic Acid and Method of Preparation", there is described a polymer having a molecular weight corresponding to an inherent viscosity of at least about 1.0 when measured as a 0.2% solution in 2 N NaOH at 25.degree. C. The method of preparation of this polymer is also described.
In commonly assigned U.S. Pat. application Ser. No. 871,280 filed concurrently herewith by Eui Won Choe, entitled "Polyacryloylaminobenzoic Acid, Polymethacryloylaminobenzoic Acid and Method of Preparation", there is described a polymer having a novel structure. The method of preparation of this polymer is also described.
The disclosures of each of the above two patent applications is hereby incorporated by reference.
The search has continued for improved processes for preparing anisotropic dopes which are useful in the production of fibers and films. This invention was made as a result of that search.